Parkinson’s disease dementia is often difficult to differentiate from dementia due to other causes and it may be due to the disease itself or as a result of the drugs taken for the disease. Dementia is a state where there is loss of previously learnt functions, or progressively impaired memory, or a marked change in personality and may be accompanied by hallucinations or depression. In Parkinson’s disease the development of dementia is a late phenomenon, often occurring 10 to 15 years after onset of the disease, and it develops in about 20% of patients. Dementia is less likely to develop in early onset of Parkinson’s disease was below 50 and more likely if it symptoms of Parkinson’s disease started after the age of 70.

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